CR-39 began the change of optical lenses from glass to plastic materials. It is
lighter weight, more impact resistant than glass lenses; thus, becoming a popular
type of material used in single vision, bifocal, and multifocal or progressive lenses.

Material is low price and easy to manufacture. It is often preferred by individuals
on a tight budget. However, because of its 1.50 index, customers with high prescription
powers are recommended to use higher index lenses such as 1.56, PC, 1.67, or 1.74
lenses.

CR39 Lenses Features are:

Fragmentation: When plastic lens breaks, it breaks into larger
fragments than their glass counterparts. Furthermore, the fragmented pieces are
not as sharp as glass.

Fogging: CR39 lenses are less likely to fog-up than glass
lenses because it responds more favorably to temperature changes.

Weight: Glass lenses are approximately 2X heavier than plastic
lenses of similar size and shape. The lighter weight provides the wearer greater
comfort.

Tinting: CR39 lenses are great for tinting. Lenses can be
tinted to virtually any color. Even lenses with variable thickness are able to be
tinted evenly.

If you want thinner, lighter lenses, and have an milder prescription, then mid index
lenses are the way to go. As prescription increases, the lenses become thicker.
Thicker lenses increase internal reflections that reduce vision quality. Furthermore,
thicker lenses add to the weight of each pair of glasses reducing comfort. Mid-Index
lenses refract the light at a greater angle allowing the wearer to have a beautifully
thin and light pair of glasses.

Mid Index Lenses Features are:

Fragmentation: When plastic lens breaks, it breaks into larger
fragments than their glass counterparts. Furthermore, the fragmented pieces are
not as sharp as glass.

Fogging: Mid Index lenses are less likely to fog-up than glass
lenses because it responds more favorably to temperature changes.

Weight: Glass lenses are approximately 2X heavier than plastic
lenses of similar size and shape. The lighter weight provides the wearer greater
comfort.

Tinting: Mid index lenses are also tintable, so you can get
that pair of sunglasses you’ve been eyeing for so long.

Polycarbonate lenses has a high index of refraction 1.59 and low density making
PC lenses 20% thinner and 25% lighter than regular plastic lenses. Polycarbonate
lenses are the most impact resistant lenses on the market. Therefore, it is the
industry standard for safety goggles, and highly recommended for kids' lenses.

Polycarbonate Lenses Features are:

Impact Resistant: Polycarbonate material was originally made
for uses on canopies covering fighter planes and then made its way into space on
astronaut visors and space shuttle windshields. Today it is readily available to
the public. It impact resistance makes the material extremely suitable for sports,
industrial safety goggles, and children's eyewear.

Scratching: The reason for polycarbonate lenses' impact resistance
is because of its "softness". Softer materials will flex instead of fragment when
met with great force. However, the property allows lenses to be scratched easily.
Therefore, every single one of our polycarbonate lenses is multi-coated with hard
coating that forms a protective layer around the lenses allowing the lenses to be
free from scratches while retaining its impact resistant qualities.

UV Protection: Polycarbonate lenses inherently carries UV
protection properties that blocks nearly 100% of the UV rays from entering the back
of the retina.

If you want thinner, lighter lenses, then high index lenses are the way to go. As
prescription increases, the lenses become thicker. Thicker lenses increase internal
reflections that reduce vision quality. Furthermore, thicker lenses add to the weight
of each pair of glasses reducing comfort. Hi-Index lenses refract the light at a
greater angle allowing the wearer to have a beautifully thin and light pair of glasses.

High Index Lenses Features are:

Fragmentation: When plastic lens breaks, it breaks into larger
fragments than their glass counterparts. Furthermore, the fragmented pieces are
not as sharp as glass.

Fogging: High Index lenses are less likely to fog-up than
glass lenses because it responds more favorably to temperature changes.

Weight: Glass lenses are approximately 2X heavier than plastic
lenses of similar size and shape. The lighter weight provides the wearer greater
comfort.

Reflections: High Index lenses have much lower internal reflection
and surface glare than glass materials.

Tinting: High index lenses are also tintable, so you can get
that pair of sunglasses you've been eyeing for so long.